const koa = require("koa");
const app = new koa();
//将use的第一个参数加到中间件数组中
app.use(ctx =>{
    //加了响应头Content-Type : text/plain
    //加了响应头Content-Length : 5
    ctx.body = "hello"
})
app.listen(8888,"127.0.0.1",()=>{
    console.log("server is running on http://127.0.0.1:8888")
})